1. Field of the Invention
The present invention relates generally to circuits for recovering stereo signals in radio receivers. More specifically, the present invention relates to techniques for recovering a pilot tone and left and right channel FM stereo signals from demodulated FM signals.
2. Description of the Related Art
Many radio transmitters radiate a transmission signal including stereo signals, such as FM stereo signals. To recover stereo signal information from the transmitted FM stereo signals, a radio receiver will demodulate and isolate the FM stereo signal information within the FM stereo signals. The transmitted FM stereo signals typically include left-minus-right (L−R) signal information, left-plus-right (L+R) signal information and a pilot tone. For example, once modulated, the left-minus-right (L−R) signal information may be centered at 38 kHz. The left-plus-right (L+R) signal information may be centered at baseband or DC. The pilot tone may be located at 19 kHz. Typically, the 19 kHz pilot tone is used to demodulate the stereo signal information into its constituent left (L) and right (R) componenets. Prior stereo decoders, however, have suffered from various inefficiencies and inaccuracies in recovering the 19 kHz pilot tone and, thereby, in recovering the stereo signal information embedded within the FM stereo signal.